A 'symphony of the sea' produced on coral reefs is being silenced by climate change, leaving baby fish unable to find their way home.

Inhabitants of the reefs usually generate a cacophony of sound that acts like a homing beacon for approaching fish, but dwindling numbers are diminishing this.

These audio cues - including shrimp clicks, damselfish chirps, and clownfish chattering - help attract young fish that are looking for a place to live or reproduce.

Without this 'coral reef orchestra', juvenile fish are being left homeless and exposed to the harsh conditions of the ocean as they struggle to find refuge.

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A 'symphony of the sea' produced on coral reefs is being silenced by climate change, leaving baby fish unable to find their way home. Inhabitants of reefs generate a cacophony of sound that acts like a homing beacon for fish, but dwindling numbers are diminishing this

A team of researchers, led by PhD student Tim Gordon of the University of Exeter, studied the hushed tones of Australia's Great Barrier Reef.

They found that the deluge of marine sounds has been silenced following recent cyclone and coral-bleaching damage.

Experiments on the famous marine habitat by the British scientists revealed the region is now significantly quieter than it was three years ago.

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Not only are the reefs quieter, they are less diverse - indicating fewer species are making their home there.

Lead author Mr Gordon said: 'It's heart-breaking to hear. The usual pops, chirps, snaps and chatters of countless fish and invertebrates have disappeared. The symphony of the sea is being silenced.

'Being able to hear the difference really drives home the fact that our coral reefs are being decimated.

'Some of the most beautiful places on Earth are dying due to human activity, and it is up to us to fix it.'

This loss of sound could have devastating consequences for the reefs and their fish communities.

A symphony of marine sound is normally produced by snapping shrimp clicks, damselfish chirps, and clownfish chattering to locate and select suitable habitat. That 'coral reef orchestra' has been silenced following recent cyclone and coral-bleaching damage

The relationship between fish and coral reefs is essential to maintaining their health, as they remove algae, facilitate coral growth, contribute to nutrient cycles and keep food webs in balance.

Scientists also found that the soundscapes of the degraded reefs are less attractive to juvenile fish. After being damaged, the reefs attract 40 per cent fewer fish.

They discovered this by building experimental reefs from coral rubble on sand flats. Underwater loudspeakers broadcast healthy coral reef sounds or degraded coral reef sounds on these artificial replicas.

It was then a matter of simply counting how many young fish were attracted to the different sounds.

WHAT IS CORAL BLEACHING?

Corals have a symbiotic relationship with a tiny marine algae called 'zooxanthellae' that live inside and nourish them.

When sea surface temperatures rise, corals expel the colourful algae. The loss of the algae causes them to bleach and turn white.

This bleached states can last for up to six weeks, and while corals can recover if the temperature drops and the algae return, severely bleached corals die, and become covered by algae.

In either case, this makes it hard to distinguish between healthy corals and dead corals from satellite images.

This bleaching recently killed up to 80 per cent of corals in some areas of the Great Barrier Reef.

Bleaching events of this nature are happening worldwide four times more frequently than they used to.

An aerial view of Australia's Great Barrier Reef. The corals of the Great Barrier Reef have undergone two successive bleaching events, in 2016 and earlier this year, raising experts' concerns about the capacity for reefs to survive under global-warming

Previous research has found that damaged reefs with healthy fish populations recover faster than reefs that have lost their fish.

Dr Harry Harding, co-author of the study, from the University of Bristol, added: 'If fish aren't hearing their way home anymore, that could be bad news for the recovery prospects of reefs.

'Fish play critical roles on coral reefs, grazing away harmful algae and allowing coral to grow. A reef without fish is a reef that's in trouble.'

Researchers measured the 'soundscape' of the Great Barrier Reef and compared it to three years ago.

In these years, the area has been besieged with cyclones and warming waters. These two factors have driven the destruction of coral reefs.

Warming seas increase the frequency and severity of coral bleaching events worldwide, as higher temperatures cause a breakdown in the relationship between corals and the algae that live there.

The relationship between fish and coral reefs is integral to maintaining healthy reefs as they remove algae, facilitate coral growth, contribute to nutrient cycles and keep food webs in balance

Previous research has found that damaged reefs with healthy fish populations recover faster than reefs that have lost their fish. Scientists found that the soundscapes of these recently-degraded reefs are less attractive to juvenile fishes by around 40 per cent

This 'zooxanthellae' algae provides energy for the corals through photosynthesis. Losing them is what causes coral to bleach and turn white.

This symbiotic relationship has evolved over millennia as a partnership that benefits both parties. However, climate change and bleaching is interfering with this balance.

Recently, up to 80 per cent of algae in some reefs has been destroyed. Bleaching events of this nature are happening worldwide four times more frequently than they used to.

Senior author Steve Simpson, associate professor in marine biology and global change at Exeter, said: 'Over the last 15 years my research group have discovered how important sound can be for fish to locate and select specific reefs.

'We have marvelled at the remarkable diversity and complexity of coral reef soundscapes. But in the last few years the reefs we know and love have died before our eyes. And the deserted and crumbling rubble fields have turned eerily quiet."

'If the reefs have gone quiet, then the chances of the next generation of fish recolonising the reefs are much reduced. Without fish, the reefs can't recover.'

Warming seas increase the frequency and severity of coral bleaching events worldwide, as higher temperatures cause a breakdown in the relationship between corals and the zooxanthellae algae that live there